Why am I getting rounded faces when combining Edge Split and Subsurf?
Edge splitting doubles the vertices and edges, effectively creating to separate parts, which then get subsurfed individually. If you need sharp edges, adjusting the Mean Crease is likely a better way. It's under Transform in the Properties panel while in Edit mode.
Here I have all the edges of the Icosphere selected, so they all get the same Crease value. You can, of course, adjust the crease for each edge individually. It applies to the currently selected edge(s).